More and more frequently, liquid or semi-liquid products are packaged in bags which are formed from one or several sheets of heat weldable plastics, the sheets being assembled by welding lines extending along their edges, so as to define in the bag a compartment for storing a liquid.
In some cases the bag is provided with a base, also made from a heat-weldable plastic sheet, which allows the bag to be placed in a generally upright position, at least temporarily.
In use, a corner of the bag is severed or cut to define an orifice through which the liquid can be poured.
The advantage of such bags is that, once empty, they can be easily disposed of inasmuch as they occupy a negligible volume, as compared to the volume occupied by rigid containers of equivalent content. Further, their destruction raises relatively less problems, both with respect to power consumption and to rejection of polluting compounds.
However, the side walls of the bag have a relatively low stiffness, which often results in the bag tilting over, and consequently spilling its contents.
Therefore, the sizes and volumes of such bags are kept relatively low and they can be used only once.
A typical example of a bag of this kind is disclosed in French Patent No. 2 436 719.
As taught in French Patent No. 1 120 327 to Rudolf EY, U.S. Pat. No. 3,523,637 TO F. J. STEC or British Patent No. 202 857 to E. J. HARBORD, the bag can be completed by an armature in order to improve its standability. In the EY bag, the armature is merely a stem extending generally centrally from the top to the base of the bag. The reinforcement of the bag is however limited, which restricts the applicability of this solution to low volume bags.
In the HARBORD bag, the armature is designed as a complete frame having rods along all the apices of the bag, some of the rods being foldable to collapse the frame when the bag is empty. This arrangement is rather complicated and practically applicable only to rectangular-shaped bags.
In the STEC bag, the armature is a relatively rigid one-piece member such as an I-beam, which is only applicable to rectangular-shaped bags and cannot be collapsed.
Other types of bags having armatures are shown in British Patent No. 802 292, U.S. Pat. No. 3,799,914, French Patent No. 2 076 112, French Patent of Addition 73 595, French Patent No. 2 171 001, U.S. Pat. No. 3,670,927, and British Patent Nos. 788 012, 651 638 and 1 048 308.